1. Field of the Invention
The invention relates to a semiconductor device composed of thyristors with a control electrode.
2. The Prior Art
In semiconductor devices the semiconductor disc, usually of silicon, with support plates, if any, applied thereon, of molybdenum or some other material having approximately the same coefficient of thermal expansion as the semiconductor disc, is normally hermetically enclosed in a box. A known box for this purpose consists of a bottom and a lid of metallic material in electrical contact with the respective side of the semiconductor disc, and of two rings of ceramic material arranged one after the other in the current direction of the semiconductor. The two rings are fixed to each other by two flanges of metallic material. Each flange is fixed to one of the rings of ceramic material, and the flanges are further directly joined to each other. If the semiconductor device is designed as a thyristor, the control electrode in the form of a wire can be fixed to the metal flanges and to the point on the silicon disc where it is to make contact. The flanges thereby act as terminals for the control electrode.
For application of a control electrode to a semiconductor disc, two fundamentally different methods are used. According to one method the control electrode is fixed to the semiconductor disc by soldering, alloying or welding. According to the other method the control electrode is held pressed against the semiconductor disc by a spring force, the semiconductor disc normally having a contact surface which is prepared in advance.